BAND GAP CHARACTERISTICS OF ONE-DIMENSIONAL QUASI-PERIODIC PHONONIC CRYSTALS WITH LAYER THICKNESS ARRANGED BY TM (THUE MORSE) SEQUENCE

Li Shang-da, Liu Yan

ABSTRACT: In order to decrease the band gap frequency, a model of one dimensional quasi-periodic phononic crystals with layer thickness arranged by TM sequence was proposed. Its band structure was investigated numerically using the transfer matrix method combined with the supercell method, then its band gap characteristics were compared with those of periodic-structure phononic crystals. Besides, the effects of filling rate and layer-thickness rate were also discussed. The results show: the band gap splitting, and decreasing phenomena can be found in this type of quasi-periodic phononic crystals; its first band gap start frequency decline nearly 50%, comparing to that in periodic-structure phononic crystals; when the rigid materials’ filling rate and the elastic materials’ approach parity, the band gap start frequency and stop frequency will come down; the first band-gap start frequency decrease with increment of layer-thickness rate. Arranging the geometrical parameters of periodic-structure phononic crystals in quasi-periodic sequence is one of the effective ways to declining the frequency of band gap, which benefits the practical ap plication of phononic crystal isolators.

Keywords: Phononic crystals, quasi-periodic, band structure, low frequency band gaps